Apparatus for burning coking coal



' Dec. 5, 1944. J. w. CARL APPARATUS FOR BURNING COKI'NG COAL Filed Jan. 13, 1941 3 Sheets-Sheet 1 DUKE F URN/NE:-

.URYDUKE ASH GREEN EUALI Eli-7 .1.

PRIDE )JRT E E Y W R m A U// E'RE E N DUAL,

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J. w. CARL APPARATUS FOR BURNING COKING COAL Filed Jan. 13, 1941 s Sheet-Sheet 2 .URVGDKE FISH GREEN UUFIL/ DUKE FUR/VINE JJRYUDKE ASH GREEN DUAL UUKE PERM/NE- IR Y DUKE EUKE FORM/NE- lNL/E'N TU ,JUH/V LU an RLJ.

11 /57 6. GREEN ED151244 Fl TTuRA/E/ Dec. 5, 1944. J. w. CARL 2,364,269

APPARATUS FOR BURNING COKING COAL Filed Jan. 13, 1941 3 Sheets-Sheet 3 68 6 67A 67 .F/ .8 69o M 4Z o A lNL/ENTU 7 dad/v 14/. EFIRLJ. 7/ 0 Q E 0 MW 72 FITTURNEY 66 Eli-7.7. Y

Patented n... s, 1944 UNITED STATES APPARATUS FOR PATENT OFFlCE' 2,364,269 BURNING conmc coAL John W. Carl, Portland, reg., asslgnor to Iron Fireman Manufacturing Company, Portland,

Oreg.

Application January 13, 1941, Serial No. 374,162

2 Claims.

burning coking coal in an underfeed stoker whereby the coke may expand freely during the coking process, thereby forming soft, friable coke which breaks apart readily.

The third object is to devise an apparatus for burning coking coal whereby green coal is brought up intocontact. with the fuel bed rapidly by an increased coal feedor an earlier coal feed causing rapid rekindling due to the gases being driven off from the green coal.

- The fourth object is to devise anapparatus for burning coking coal whereby the volume of the fuel bed required for the most efiicient combustion is quickly restored by an accelerated coal feed or by a preliminary coal feed.

The flfth object is to devise an apparatus whereby the fissures in the fuel bed are filled by the increase in coal feed inproportion to the burningrate 'as brought about by the increased coal feed.

'I'hesixth object is to provide an apparatus whereby there will be a rapid recovery of the fire after an "off period in" order to restore it to its most efficient condition. I The seventh object is to provide an apparatus of the class described. which will lower th fuel and electrical consumption for a given heat output.

The eighth object is to provide an apparatus of the class described-by means of which it will be possible to obtain a quicker recovery of room tem peratures and steam pressures.

The ninth object is to provide an apparatu of the class described which will reduce th fly ash due to better fuel bed conditions. I

The tenth object is to construct an apparatus of theclass described which will minimize hold fire problems and hold fire fuel consumption due to quick reklndling of the fire.

\The eleventh object is to provide an apparatus of the class described especially adapted to normal stoker operation where the stoker operates at varying lengths of time and at varying intervals wherein the fuel feeding rate during operation of the stoker will be increased from the time of a predetermined change in a combustion condition to the time of a predetermined opposite change in condition.

The twelfth obiectis to provide an apparatus of the class described wherein the fuel feedins rate will be increased for a predetermined time (cine-42) starting at the commencement of'a swker operation.

The thirteenth object is to provide an apparatus of the class described wherein the fuel feeding rate will be increased for a time starting at the commencement of a stoker operation and ending after a predetermined change in a combustion condition.

The fourteenth object is to provide an apparatus of the class described wherein the fuel feeding rate will be increased for a time starting at the commencement of a stoker operation and ending after the attainment of a predetermined combustion condition.

These. and other objects are accomplished in the manner set forth in the following specification as illustrated in the accompanying drawings,

green coal to dry coke and representing a condi-.

tion found after a banking period. 7

the coke column breaks down.

Fig. 3 is a viewsimilar to Figs. 1 and 2 in which it is shown that as the coke column of Fig. 2 continues-to grow it becomes unbalanced as a column and the top of the column breaks off in masses too large for eflicient or controlled combustion.

Fig. 4 isv a somewhat fragmentary section through a retort illustrating the first stage or condition during a start of operating after bankingperiod when my method and apparatus are employed, during which time the stoker is operating at an increased, or in some cases, an earlier coal feed.

Fig. 5 is a view similar to Fig. 4 also showing my method and apparatus for the flre condition after the stoker has returned to normal coal feed.

Fig. 6 is a view similar to Fig. 5 also showing my method and apparatus and showing a third stage of operation which is a portion of the continued normal operation illustrating the manner in which the coke splits apart and wherein there 50 is maintained a compact fuel bed resulting combustion efllciency,

Fig. 7 is a diagrammatic view showing the preferred form of circuit involving the control and response to changes in stack temperature.

Fig. 8 is an enlarged fragmentary view show- Fig. 2 is a view similar to Fig. 1 also showing the prior art condition in its second stage before in high Similar numerals refer to similar partsthroughout the several views.

Before entering into an explanation of this invention, it must be understood that the apparatus and arrangements of Fig. '7 can be varied to use my method of operation in several ways.

In Fig. 7, the instrument responsive to combustion condition is shown as a stack switch 35 although any other type or location of control could be used, provided only that it be responsive to combustion condition as desired. And of course the stack switch shown could be either of the type having an adjustable fixed lower limit or an adjustable fixed upper limit, or of the type, also well known, which operates in accordance with a predetermined rise or fall in stack temperatures.

Again it should be noted that the control 36 is of the well known recycling, refueling type in which the refueling mechanism returns to zero and starts its refueling timing at the end of each burner operation.

With this arrangement, the increased fuel-air ratio would be established at the commencement of a burner operation and would continue until the stack switch 35 returned the fuel-air ratio to normal. Or, again, the stack switch 35 could be short circuited and the increased fuel to air ratio would continue for a definite predetermined time after the commencement of a burner operation.

Referring in detail to the prior art, Figs. 1 to 3 inclusive, there is shown a retort [5 upon which is mounted a set of tuyeres I6 about which is disposed the oasing ll forming a plenum chamber it from which air can escape through the tuyere openings l9 into the burning fuel.

For the purpose of illustration, the air supply pipe is shown entering the plenum chamber it from the side opposite the coal tube 2| although in common practice they both enter the same side of the casing ll. A coal feeding worm 22 is mounted in the tube 2| and extends into the retort l5 and is driven by a mechanism and in a manner which will be described later. A burning surface 23 is formed around the uppermost tuyere 24 slightly below its side outlets 25.

In this form of the device, green coal 26 is drawn from a source of supply not shown) and fed into the retort It by means of the coal feeding worm 22. In Fig. 1, which represents the start of an operation after a banking period, there remains a body of green coal 26 which extends to the bottom of the dry coke column 2'! which was left behind from the previous operation, the mass of this column of coke 21 being bonded together by products of distillation ranging from green coal to dry coke.

On the burning surface 23 are some ashes 28 upon which lie pieces of dry coke 29 which have broken off of the coke column 21 during the preceding operation. Special attention is drawn to the existence of blow holes 26 formed around the column 21, which not only tend to permit the air to escape without being forced through the fuel, but also tend to cool off and further solidify the coke column 21.

The condition illustrated in Fig. 2 shows with average accuracy a condition prevailing when burning coking coal after a normal feeding operation is resumed. Here the coke column 2l--A has increased in height, having been built up from is not forced into a burning relationship with the forming coke but actually serves to cool the same below the burning temperatures. i

In Fig. 3 it will be seen that the coke 21--B has fallen over into a pile toone side of the central coke column 21, still leaving large blow holes or voids 30 through which the combustion air can escape to the stack, thereby resulting in inefiicient combustion of fuel which becomes more noticeable during the burning of coking coal when the stoker operation is not continuous.

Referring now to my invention, it .will be noted that Fig. 4 represents the condition wherein the lower level of the coke 3! has receded during a banking period to a point below the tuyere openings I9. Fig. 4 represents the condition existing at the start of a run in which the stoker operates at an increased rate of coal feed until a pre-determined rise in stack temperature occursthe' air supply being set for normal coal feed.

In Fig. 5, which represents the condition at the close of an excess feed or a return to normal coal feed and a continuation ofnormal air feed, it will be seen that the condition of the fire bed is such as to insure high combustion efliciencythat is, the coke in all its forms is distributed over the entire burning surface requiring that the air from the tuyre 16 come into intimate contact with all of the fuel. There are no voids through which the combustion air can escape without performing its duty.

In Fig. 6 is illustrated a condition of continued normal operation wherein it will be seen that the coke 2'|C crumbles or breaks up as it rises without formation of a high coke column and without the formation of large voids through which air can escape to the stack without properly combining with the fuel. I

It will be noted that Fig. 6 illustrates an ideal fire bed condition brought about by the practice of my method and the employment of my apparatus as compared to the corresponding prior art condition shown in Fig. 3.

Figs. 1 to 6 are not based on theory but are compiled on actual operating conditions.

In Fig. 7 there is shown in fragmentary section a furnace 32 in which is disposed the retort casing l1 and the burning surface 23. The gaseous products of combustion pass through the smoke outlet 33 into the smoke stack 34 with which is associated a normally open'stack switch 25 which is responsive to changes in temperature in the stack 34, tending to close at a predetermined minimum temperature and open at a predetermined maximum temperature. The stack switch 35 may be of any suitable type of which numerous forms are now on the market in which the switch opens on a predetermined rise in temperature and closes on a predetermined drop in temperature, this switch being preferably of the type containing the drag eliminating feature, a common form of which is illustrated in the Klingel Pat. No. 1,403,963 wherein temperature changes are anticipated. v

Associated with the thermostatic stack switch 36 is an intermittent 'stoker control switch 26 which is of the type operating on a time'interval contactor which will cause the stoker'motor 62 to be intermittently operated for hold flre purposes during periods when'there are no calls for heat from the furnace 32 by the thermostat "A.

For example, controls of this class permit the stoker to be operated in response to temperature or pressure requirements at the point of delivery cuit open or closed during that measured interval of time.

It will be understood that this time stoker control switch is employed to actuate the solenoid 56. That is, to cause an excessive feeding of fuelduring a predetermined definite period of time for the reasons stated. Such devices are so well known as to require further explanation thereof unnecessary here, but it must be understood that the controls herein described will not function merely to produce an excessive feeding of coal at the commencement of a firing operation when the stack temperature reaches a predetermined minimum, but at the commencement of any firing period following a predetermined drop in stack temperature.

The usual line switches and fuses are contained within the stoker control switch 36, to which power is supplied from the line 38. For the purpose of this disclosure there are indicated the terminals 39 and 40 of the stoker control switch 36.

Associated with the furnace 32 and connected with the coal tube 2| is a gear case 4| in which is disposed the shaft 42 of the coal feeding worm 22. The shaft 42 journals in the anti-friction bearing 43 and in the bushing 44 which is mounted in the cover 45 of the casing 4|.

Rotatably mounted on the shaft 42 is a worm wheel 46 which meshes with a worm 41 on' whose shaft 48 is mounted a pulley 49 whose belt 50 passes around the pulley of the motor 52. The shaft 48 has als mounted thereon a fan contained within the casing 53 from which air is conducted through the air supply pipe to the plenum chamber l8.

One terminal of the motor 52 is connected by a lead 54 to the terminal 39 of the time interval contactor 36 and to one side of the thermostatically operated stack switch 35, The second terminal of the motor 52 is connected by the lead 5: to the terminal 49 of the stoker control switch 3 Mounted on the casing 4| is a solenoid 56, one side of which is connected by the lead 51 to the lead 55 and the other side of which-is connected by the lead 58 to the second terminal of the switch 55.

Merely to illustrate a. representative way of varying the proportion of air and fuel delivered to a furnace, there is shown the mechanism illustrated in Figs. 8, 9 and 10 in which a ratchet wheel 59 is keyed on the shaft 42. The ratchet wheel 59 which drives the coal feeding worm 22 .is held against backward movement by the holding pawl 69 which is secured to the casing 4| by Rotatably mounted on the hub 62 of the ratchet wheel 59 is a cam 63 whose outermost lobe- 64 extends beyond the outside diameter of the. ratchet wheel 59. The cam 63 has secured thereto an operating lever 65 which through a link 6'|A is connected by the pin 66 to the core 61 of'the solenoid 56. The pin 66 also connects the lever 65 to the link 68 which is connected to a bell crank lever 69 whose fulcrum pin 10 is attached to the cover 45. The weight M is adjustably held on the lever arm 12 by means of the set screw 13.

The action of the weight H causes the lever 65 to be urged in a counter-clockwise direction when viewed as in Fig. 10, while the closing of the circuit through the leads 54 and 58 by the switch 35 in response to a drop in stack temperature will cause the solenoid 56 to be energized and the lever 65 to be moved in a direction which will raise the weight 1 I The hub 14 of the worm 46 is eccentricand has mounted thereon a slide block 15 which is mounted between the parallel guides 16 of the rocker frame 11 which is pivoted on the pin I8 which is mounted on the inside of the cover 45. On the upper end of the frame 11 is mounted the driving pawl 19.

While the pawl 19 normally engages the teeth of the ratchet wheel 59 during only a portion of its travel due to the fact that it is held out of engagement by the lobe 64, it can be seen that when the solenoid 56 moves the lever 65 and the cam 63 to the right in Fig. 10, more of the teeth of the ratchet wheel 59 will be uncovered and more coal will be fed to the fire at each revolution of the wheel 46 although the quantity of air supplied in the same period remains the same.

In other words, whenever a stoker period of operation commences at a time when a stack temperature is subnormal, the rate of initial coal feeding is increased considerably beyond the abil-- ity of the incoming air to consume the coal, thereby causing a rapid rekindling of the fire without creasing the proportion of fuel delivered, and

means responsive to a predetermined rise in stack temperature for returning the proportion to normal.

2. An apparatus of the class described havin in combination a conveyor for moving coal into a retort, a fan for supplying air to the retort, means for establishing a desired ratio of air and coal delivered to the retort to meet normal firing requirements, in which the air delivered by the stoker fan is set for the normal feed rate and maintained constant throughout the entire operation of the stoker, means for intermittently operating the coal and air feeding mechanism for hold fire purposes and means responsive to subnormal stack temperatures for producing excessive feeding of fuel during the portions of each firing period when stack temperatures are subnormal. 

